The recent retreat of glaciers in the world

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1 The recent retreat of glaciers in the world Consequences for the global environment Dr Bernard Francou Director of Research Emeritus Grenoble-Alpes University - France

2 Glaciers are part of the cryosphere Cryosphere is very sensitive to climate change Polar Ice sheets and ice shelves Sea ice (summer/winter) Mountain glaciers Permafrost Snow covers 52-55% of land areas UNEP-GRIP

3 Major components of the cryosphere % of the land areas 5-7 % of sea surfaces From IPCC % of ice volumes in the polar ice sheets

4 Antarctica East West Peninsula - Sea ice : 30 M km 3 5 main components 5 1. Eastern ice sheet : 88 % of land ice volume. 75 % of outlet glaciers falling on ice shelves Western ice sheet : 10 % of ice volume 3. Peninsula : 2 % of Antarctica ice volume 4. Ice shelves : 1.2 M km² 5. Sea ice : 18 M km² in September (seasonal maximum)

Antarctica better estimations of mass balance of polar ice sheets since the early 2000 A contrasted mass balance according to the regions Mc Millan et al. 2014 GRL Shepherd et al.

decades) Western ice sheet : becoming unstable (75% of ice loss of Antanrctica). Main processes: acceleration of outlets glaciers and retreat of grounding lines (tens of km!

5 Antarctica better estimations of mass balance of polar ice sheets since the early 2000 A contrasted mass balance according to the regions Mc Millan et al GRL Shepherd et al Science Continent (30 M km 3 ) Eastern ice sheet : stable or slightly positive Due to increasing precipitation close to the coasts (sea and atmospheric temperature rose up during the last decades) Western ice sheet : becoming unstable (75% of ice loss of Antanrctica). Main processes: acceleration of outlets glaciers and retreat of grounding lines (tens of km!) Peninsula : Rapid retreat of glaciers and desintegration of ice sheelves (25 % of ice loss of Antarctica. Strong temperature increase (+2,5 C since 1950) Max. loss of ice Mean loss estimated to ~50-60GT ice/year over the period CRYOSAT-2

Antarctica West Antarctica region and peninsula loss mass at a strong rate

Breakdown of the Larsen B (Peninsula) Winter 2002 Ice shelves : 1.2 M km².

basal melting and 2) calving) NASA 30 km Breakdown of the Pine Island

6 Antarctica West Antarctica region and peninsula loss mass at a strong rate : can ice sheets become unstable if ice shelves break down? Breakdown of the Larsen B (Peninsula) Winter 2002 Ice shelves : 1.2 M km². The biggest are still stable, only the small ones are retreating by : 1) basal melting and 2) calving) NASA 30 km Breakdown of the Pine Island Glacier (Western Antarctica) October-November 2013 Grounding line retreated 31km ( )

7 King, 2014 Nature IPCC 2013 Antarctica sea ice seasonal and thin Austral sea ice is globally stable or slightly increasing! + 1,5 % per decade (not everywhere) Why??? Red: : increasing sea ice

Hanna et al., 2011 Greenland melts at fast rates Greenland is ~10 times less than Antarctica in volume 3 M km 3 i.e. equivalent of 7 m sea level (in case of complete melting) Why Greenland is becoming vulnerable?

8 Hanna et al., 2011 Greenland melts at fast rates Greenland is ~10 times less than Antarctica in volume 3 M km 3 i.e. equivalent of 7 m sea level (in case of complete melting) Why Greenland is becoming vulnerable? strong warming of the Arctic zone since 30 years : +2,4 C at Summit (3200 m) Important warming in the North Atlantic ocean (through the Gulf stream) Rapid retreat of sea ice and snow cover at high latitude over the 30 last years : strong positive feedback with the albedo Meteorological station network in 2011

Greenland : surface melting and ice discharge are ~ equivalent Greenland loss : ~142 MGt ice/yr (equivalent of 0.39mm/yr of sea level rise from 1992 to 2011) Two processes are dominant : 1.

9 Greenland : surface melting and ice discharge are ~ equivalent Greenland loss : ~142 MGt ice/yr (equivalent of 0.39mm/yr of sea level rise from 1992 to 2011) Two processes are dominant : 1. melting rates on the surface have increased due to the recent air warming (~50% of the ice loss). In 2012, melting was observed for the first time at the Summit station) 2. Ice discharge in ocean has increased thank to an acceleration of the outlet glaciers (50% of the ice loss) Shepherd et al Science Melting in contact with ocean water was underestimated

10 Greenland: a more and more negative mass balance Denis Sarrazin CNSAN Acceleration of the outlet glaciers, retreat of the grounding line and melting on contact with ocean NASA 2010 Disintegration of ice shelves Ward Hunt (nord) Jakobshawn Isbrae : km NASA Jakobshawn Isbrae (6 to 12 km/yr from 1992 to 2003) Increasing melting at the surface : 30-50% of Greenland in summer in average (98% in 2012)

The most impressive picture of Arctic warming is the rapid retreat of sea ice Loss of 40% area and 50% volume during the last 30 years Median 1979-2000 ~ - 11% per decade during

11 The most impressive picture of Arctic warming is the rapid retreat of sea ice Loss of 40% area and 50% volume during the last 30 years Median ~ - 11% per decade during the period The pack ice is becoming thinner (the «old ice» is disappearing) Why? 1) Increasing summer temperature and 2) Important albedo feedback 2012 NSIDC IPCC 2013

12 Important consequences of the arctic sea ice collapse Warming feedback (albedo) A disaster for ecology and traditional societies New maritime routes, new resources and potential conflicts

13 As sea ice, the seasonal snow cover has been reduced during the last decades. Bernard Francou Massif de Chartreuse Préalpes françaises

Evidences of the snow cover decline in the northern Hemisphere 1986 Deterioration of the snow cover in March-April from the 1980s Deterioration

14 Evidences of the snow cover decline in the northern Hemisphere 1986 Deterioration of the snow cover in March-April from the 1980s Deterioration faster in June Since , loss of 5 days/decade =(25 days), particularly in spring Anomaly of snow cover extension in relation to GIEC, 2013

Glaciers and ice caps Around 200 000 glaciers in the world [equivalent of 41 cm of sea level] Glaciers and ice caps currently represent the major contribution to sea level rise (out of thermal

15 Glaciers and ice caps Around glaciers in the world [equivalent of 41 cm of sea level] Glaciers and ice caps currently represent the major contribution to sea level rise (out of thermal expansion) : 0,76 mm/an Great diversity (from poles to tropics) The huge «oceanic glaciers» (calving directly to ocean) have the major impact on the sea level rise (North Canada, Alaska, Patagonia, Svalbard ) «Continental glaciers «(high elevation) are retreating slowly and their impact to sea level rise is less The total loss of glaciers is estimated to be ~ 30cm/yr in water equivalent Tierra de Fuego B.F.

16 Mountain glaciers and ice caps A coherent (negative) signal coming from 57 glaciers measured in the world AMERICA the world ARCTIC EUROPE ASIA Sources: WGMS + Glacioclim The great majority of glaciers experience a negative balance since or

the present climate 2020 2030 Vincent et al.

(1958-2012) : ~0,8 km Main cause : increasing summer

17 Why are glaciers retreating? Glaciers shrink because they are not in equilibrium with the present climate Vincent et al., Retreat of La Mer de Glace, French Alps ( ) : ~0,8 km Main cause : increasing summer temperature Simulations for 2020, 2030 and 2040 : The glacier continues to decline even if temperature remains steady

18 Christian Vincent Mer de Glace French Alps Model

19 Et Aletsch glacier (Switzerland) The bigest glacier of the continental Europe «Steady scenario» : volume loss : 40% Scenario +2 C (2100) retreat : 10 km (of the 22 km) and 90% volume loss

20 CHACALTAYA glacier (5400m, Andes of Bolivia) Pictures of a disappearing glacier : BF 2000 BF 2003 BF 2005 BF 2009 PG 2010 PG

The global warming (1980-2015) is the main cause of the current decline of glaciers in the world Combined temperature (continents et oceans) combinés) depuis 1850 IPCC, 2013 +0,8 C (averaged) since

21 The global warming ( ) is the main cause of the current decline of glaciers in the world Combined temperature (continents et oceans) combinés) depuis 1850 IPCC, ,8 C (averaged) since 1880 and +0,7 C since1970 (acceleration) Temperature increased more on continent than in oceans. (mesures + models). Goddard Institute for Space Studies IPCC, 2013 Warming is amplfied on continents and in polar regions

22 Multiple impacts of ice recession

23 What is the impact of ice retreat on sea level at global scale? PRESENT sources Thermal expansion 1,1 ± 0,3 Glaciers, ice caps 0,76 ± 0,4 Greenland 0,33 ± 0,08 Antarctica 0,27 ± 0,11 Continental waters 0,38 ± 0,11 Sum of contributions 2,80 ± 0,5 Observations (by altimetry) 3,2 ± 0,4 FUTURE 1 m Individual contributions to sea level since 1993 and altimetric observations (in mm) Source: Casenave et al., 2015 Increasing sea level depending on warming scenarii (RCP) IPCC, 2013 Ice component : 49% Glacier component (of 49%) : 56% Contribution of glaciers could remain dominant in 2100 (except if contributions of Greenland and West Antarctica strongly increase!)

24 What are the other impacts of ice and glacier recession Increasing warming: a planet with less covered ice and snow areas absorbs more solar energy (albedo feedback) ( polar regions) Water resource: glaciers and snow covers are natural reserves of water which regulate runoff in mountain basins ( Andes, US. Rockies, Alps, Himalaya, Tien Shan, etc.) Natural hazards: the risk of glacier lakes burst out and glacier avalanches increase (Peru, Nepal, Alps). Impact on ecological equilibrium and traditionnal indigenous survivals (Inuit populations) New routes, new economic perspectives and new boundaries around the Arctic region (new resources but politic tensions increase)

25 GRACIAS! MS - Training course La Paz NASA Visible Earth

The State of the cryosphere

The State of the cryosphere Course outline Introduction The cryosphere; what is it? The Earth; a unique planet Cryospheric components Classifications Lecture outlines The State of the cryosphere The State